Explain the pattern oftinheritance of haemophilia in humans. Why is the possibility of a human female becoming haemophilic extremely rare ? Explain.

Explanation

Haemophilia is a sex-linked (X-chromosome) recessive disorder which shows its transmission from unaffected carrier female to some of the male progeny.
Female is carrier (heterozygous `XX^h` female) transmits it to her sons and sufferer (homozygous `X^hX^h`) and transmit the disease to all her sons. The possibility of a female becoming haemophilic is rare because mother of such a female has to be at least carrier and the father should be haemophilic.